Shared Medium Flashcards
How do we connect 2 computers?
connect cable from one to another and agree the format used to transfer over network
what are the drawbacks of connecting more than 2 computers using simple approach?
need more cables which is expensive and safety hazard also unpractable
what increases as we add more computers?
connections
What would need to be available for more computers?
space ports, new cables
What is a better way for connecting?
shared medium
how does shared medium approach work?
instead of every computer having a cable to every other computer they only have 1 cable connected to a shared medium
what is a medium?
it can be anything like cable, radio wave etc
how is shared medium more simpler?
for any new computer we just add a new connection to the shared medium
what are the advantages of shared medium?
any computer can talk to another
what are the disadvantages?
only one computer can talk at any time and if all transmit at same time then data can collide and become corrupted
how do we avoid collisions?
use access control and make it so only control can send and rest listen
what is access control?
control who can send on the medium and how long they can send for
why do we control the length they can send for?
if not one device could monpolise the whole resource
how do we avoid a computer monopolising
break the communication into packets then allow each computer to send a packet in turn
so what is packet switching?
split data into small packets
each packet is sent individually across shared medium
if message bigger than packet break it into smaller packets
reassemble at the other end
need destination address
need a packet header
